======================================
| xx__-> [   36.062058][   T12] ==================================================================
| [   36.062357][   T12] BUG: KASAN: slab-use-after-free in kobject_put (lib/kobject.c:733)
| [   36.062609][   T12] Read of size 1 at addr ffff888007f896ac by task kworker/u16:0/12
| [   36.062846][   T12]
[   36.062936][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   36.062938][   T12] Workqueue: netns cleanup_net
[   36.062944][   T12] Call Trace:
[   36.062946][   T12]  <TASK>
[   36.062949][   T12]  dump_stack_lvl (lib/dump_stack.c:123)
[   36.062954][   T12]  print_address_description.constprop.0 (mm/kasan/report.c:379)
[   36.062961][   T12]  ? kobject_put (lib/kobject.c:733)
[   36.062965][   T12]  print_report (mm/kasan/report.c:483)
[   36.062969][   T12]  ? kobject_put (lib/kobject.c:733)
[   36.062972][   T12]  ? kasan_addr_to_slab (./include/linux/mm.h:1245 mm/kasan/../slab.h:191 mm/kasan/common.c:47)
[   36.062975][   T12]  ? kobject_put (lib/kobject.c:733)
[   36.062978][   T12]  kasan_report (mm/kasan/report.c:597)
[   36.062983][   T12]  ? kobject_put (lib/kobject.c:733)
[   36.062989][   T12]  kobject_put (lib/kobject.c:733)
[   36.062992][   T12]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   36.062997][   T12]  ? irqentry_exit (kernel/entry/common.c:215)
[   36.063001][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   36.063005][   T12]  ? generic_xdp_install (net/core/dev.c:11630)
[   36.063012][   T12]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   36.063019][   T12]  ? netns_get (net/core/net_namespace.c:223)
[   36.063022][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   36.063027][   T12]  cleanup_net (net/core/net_namespace.c:698)
[   36.063030][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[   36.063034][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   36.063040][   T12]  process_one_work (kernel/workqueue.c:3268)
[   36.063048][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   36.063053][   T12]  ? assign_work (kernel/workqueue.c:1206)
[   36.063057][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   36.063063][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[   36.063066][   T12]  kthread (kernel/kthread.c:463)
[   36.063070][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   36.063074][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   36.063082][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   36.063090][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   36.063093][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   36.063096][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[   36.063099][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   36.063102][   T12]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   36.081633][   T12] refcount_t: underflow; use-after-free.
| [   36.081808][   T12] WARNING: CPU: 3 PID: 12 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [   36.082161][   T12] Modules linked in: nft_masq nft_chain_nat nf_nat nft_ct nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables veth
| [   36.082903][   T12] Tainted: [B]=BAD_PAGE
[   36.083095][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   36.083301][   T12] Workqueue: netns cleanup_net
[   36.083476][   T12] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[   36.083688][   T12] Code: 83 90 02 80 fb 01 0f 87 95 6b d6 fe 83 e3 01 0f 85 51 ff ff ff c6 05 b1 83 90 02 01 90 48 c7 c7 a0 de 25 bb e8 c2 8b 15 ff 90 <0f> 0b 90 90 e9 33 ff ff ff 48 89 df e8 f0 34 a1 ff e9 ba fe ff ff
All code
========
   0:	83 90 02 80 fb 01 0f 	adcl   $0xf,0x1fb8002(%rax)
   7:	87 95 6b d6 fe 83    	xchg   %edx,-0x7c012995(%rbp)
   d:	e3 01                	jrcxz  0x10
   f:	0f 85 51 ff ff ff    	jne    0xffffffffffffff66
  15:	c6 05 b1 83 90 02 01 	movb   $0x1,0x29083b1(%rip)        # 0x29083cd
  1c:	90                   	nop
  1d:	48 c7 c7 a0 de 25 bb 	mov    $0xffffffffbb25dea0,%rdi
  24:	e8 c2 8b 15 ff       	call   0xffffffffff158beb
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	e9 33 ff ff ff       	jmp    0xffffffffffffff66
  33:	48 89 df             	mov    %rbx,%rdi
  36:	e8 f0 34 a1 ff       	call   0xffffffffffa1352b
  3b:	e9 ba fe ff ff       	jmp    0xfffffffffffffefa

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	e9 33 ff ff ff       	jmp    0xffffffffffffff3c
   9:	48 89 df             	mov    %rbx,%rdi
   c:	e8 f0 34 a1 ff       	call   0xffffffffffa13501
  11:	e9 ba fe ff ff       	jmp    0xfffffffffffffed0
[   36.084318][   T12] RSP: 0018:ffffc900000c7a08 EFLAGS: 00010282
[   36.084531][   T12] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[   36.084768][   T12] RDX: 0000000000000002 RSI: 0000000000000004 RDI: 0000000000000001
[   36.085082][   T12] RBP: 0000000000000003 R08: 0000000000000000 R09: fffffbfff777e220
[   36.085327][   T12] R10: 0000000000000003 R11: ffffc900000c7580 R12: 0000000000000001
[   36.085574][   T12] R13: dffffc0000000000 R14: dead000000000122 R15: dead000000000100
[   36.085839][   T12] FS:  0000000000000000(0000) GS:ffff88807936c000(0000) knlGS:0000000000000000
[   36.086195][   T12] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   36.086407][   T12] CR2: 00007f7a8832b000 CR3: 000000000d735001 CR4: 0000000000772ef0
[   36.086648][   T12] PKRU: 55555554
[   36.086773][   T12] Call Trace:
[   36.086895][   T12]  <TASK>
[   36.087049][   T12]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   36.087235][   T12]  ? irqentry_exit (kernel/entry/common.c:215)
[   36.087418][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   36.087578][   T12]  ? generic_xdp_install (net/core/dev.c:11630)
[   36.087739][   T12]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   36.087905][   T12]  ? netns_get (net/core/net_namespace.c:223)
[   36.088134][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   36.088300][   T12]  cleanup_net (net/core/net_namespace.c:698)
[   36.088468][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[   36.088631][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   36.088791][   T12]  process_one_work (kernel/workqueue.c:3268)
[   36.089006][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   36.089172][   T12]  ? assign_work (kernel/workqueue.c:1206)
[   36.089327][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   36.089503][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[   36.089665][   T12]  kthread (kernel/kthread.c:463)
[   36.089782][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   36.089955][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   36.090125][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   36.090281][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   36.090444][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   36.090602][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[   36.090762][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)


Finger prints:
print_report:kasan_report:kobject_put:netdev_run_todo:ops_undo_list
refcount_warn_saturate:netdev_run_todo:ops_undo_list:cleanup_net:process_one_work